1. Field of the Invention
The invention relates to a method for detecting rain on a windshield, whose degree of wetting is determined with at least one sensor value. In addition, the invention also relates to a device for detecting rain on a windshield, with at least one rain sensor, which is allocated to a windshield wiper system for the windshield, and a motor vehicle with such a device.
2. Brief Discussion of the Related Art
In motor vehicles, rain sensors are most often coupled with an activation of the windshield wiper system, so that once rain hitting the windshield has been registered or a predetermined degree of windshield wetting has been detected, windshield wipers are automatically activated. The most common rain sensors today are those based on optoelectric measurement. These rain sensors most often exhibit at least one light source and at least one detecting photodiode, wherein the light source sends out an optical signal, which is reflected in a predetermined detection range on the windshield, and the reflected optical signal is detected by the photodiode. A differential value is then derived from the transmitted and detected optical signal, based upon which the degree of wetting for the detection range of the windshield is determined. However, the disadvantage is that the detection range of the optoelectric rain sensors only detects a small section usually measuring about 2 cm2 of the windshield. Therefore, rain is inaccurately detected primarily at the beginning of showers, since a larger amount of rain might already have hit the windshield without the detection range having been sufficiently wetted. In addition, the spray from oncoming traffic is only inadequately detected, if at all.